Vacuum sheet stripper

ABSTRACT

A transport mechanism for stripping a copy sheet from a photoconductive surface and transporting the copy sheet therefrom. The transport comprises a plurality of perforated belts mounted for movement relative to a vacuum plenum, a roll assembly being provided on the transport adjacent the photoconductive surface to move the stripped copy from the strip point, a plurality of vacuum stripping ports being disposed adjacent the roll assembly, the vacuum ports being canted at an acute angle relative to the lead edge of the copy sheet to provide air flow thereto in a direction opposite to the direction of copy sheet movement.

United States Patent Bigenwald 1 July 22, 1975 VACUUM SHEET STRIPPER Primary ExaminerEvon C. Blunk P l 1d, N.Y. [75] lnvmor John J Blgenwald en Asszsranl Exammer-Robert Sa1fer [73] Assignee: Xerox Corporation, Stamford, Conn. [57] ABSTRACT [22] Filed; 20,1973 A transport mechanism for stripping a copy sheet from a photoconductive surface and transporting the [21] APP]- N05 427009 copy sheet therefrom. The transport comprises a plurality of perforated belts mounted for movement rela- 52 US. Cl. 271/174; 271/197; 271/010. 2 tive to a vacuum P a roll assembly being p 51 1m. (:1. B65h 29/56 vided Oh the transport adjacent the photoconductive 58 Field of Search 271/1310. 2, 174, so, 197, surface to move the pp py from the strip p 2 133 1 4 194 19 172; a plurality of vacuum stripping ports being disposed 355/3 226/5 adjacent the roll assembly, the vacuum ports being canted at an acute angle relative to the lead edge of [56] References Cited the copy sheet to provide air flow thereto in a direc- UNITED STATES PATENTS tion opposite to the direction of copy sheet movement. 3,674,257 7/1972 Neeb et a1. 271 194 x 3,743,403 7/1973 Sanza 271/1310. 2 4 Clam, 4 Drawmg Flgures 3,774,907 11/1973 Borostayn 271/D1G. 2

PATENTED JUL 2 2 I975 SHEET SHEET PATENTED JUL 2 2 I975 V N QM VACUUM SHEET STRIPPER BACKGROUND OF THE INVENTION In conventional xerography, a xerographic surface comprising a layer of photoconductive insulating material affixed to a conductive backing is used to support latent electrostatic images. In the process, the xerographic surface is electrostatically charged and the charged surface is then exposed to a light pattern of the image being reproduced to thereby discharge the surface in the areas where the light strikes the surface. The undischarged areas of the surface thus form an electrostatic charge pattern in conformity with the configuration of the original pattern.

The latent electrostatic image may then be developed by contacting it with a finely divided electrostatically attractable material, ordinarily a pigmented resinous powder, referred to herein as toner. The toner particles are attracted to the electrostatic image from the carrier to produce a visible toner image on the xerographic surface.

After the image is developed, a transfer member, ordinarily copy paper, is caused to move in synchronized contact with the photoconductive surface. During this time an electrical potential opposite from the polarity on the toner is applied to the side of the paper remote from the photoconductive surface to electrostatically attract the toner image from the xerographic surface to the copy paper. The copy paper, which is an insulator, retains the charge while inducing a reverse charge on the non-discharged areas of the xerographic surface. This charge orientation creates an electrostatic bond between the paper and the xerographic surface. Removal of the copy sheet which is electrostatically bonded to the surface, without disturbing the toner image loosely adhering thereto, has long been a problem in the xerographic art.

In order to separate the copy sheet from the xerographic surface, the charge on the copy sheet may be neutralized or reduced with a corona discharge device while the sheet is on the xerographic surface. Assuming the copy sheet is partially neutralized thereby, a vacuum stripping device may be employed for pulling the leading edge of the copy sheet from the xerographic surface for subsequent movement of the copy sheet away from the xerographic surface by a suitable paper transport.

For optimum stripping, the vacuum stripping ports must be as close to the photoreceptor as possible, and must be located in close proximity to the area of the paper being sprayed by corona from the detacking corona emission device. Further, the transport belts, which are to convey the stripped paper from the photoreceptor must also be located as close as possible to the vacuum ports, the corona emission device, and the photoreceptor.

In the normal operation of a xerographic copy machine, a number of variables which effect sheet stripping may be encountered. For example, the machine may be adapted to handle a variety of copy paper stock including the entire range of commercially available paper weights. Further, the machine may operate in an environment subject to a wide range of relative humidity. Both the weight and the water content of the paper have a dramatic effect on paper stripping.

A third variable that may be encountered in a copy machine which may effect stripping is the efficiency of the detacking corona emission device. As toner particles from within the machine are unavoidably deposited on the corona emission device, the efficiency of the device drops off. As the efficiency drops off, the electrostatic force holding the sheet on the photoreceptor increases, requiring an increased stripping force. The foregoing are just a few of the variables encountered in attempting to provide a stripping device operable under all conditions to which the machine may be subjected.

To minimize the possibility of a mis-strip, a fairly large vacuum must be provided at the stripping ports. However, as the vacuum level is increased, it is obvious that the power requirements to produce the high vacuum increase as does the noise generated by the flow of air through the vacuum ports. Further, at high vacuum, undesirable air currents may be set up within the machine which may draw toner particles into the stripping area causing premature and undesirable toner particle deposition on elements of the stripping device and the corona detacking device, which toner not only effects the efficiency of the devices but may result in toner deposits on the underside of the copy being produced.

It is, therefore, an object of this invention to provide a vacuum stripping transport for use in a copy reproduction machine having improved vacuum stripping ports for greater stripping efficiency at low vacuum levels.

SUMMARY OF THE INVENTION The present invention relates to a reproduction machine wherein a copy sheet is electrostatically tacked to a moving image support member, the machine including a transport apparatus for removing the copy sheet from the support member and transporting the sheet toward the next station in the machine, the transport apparatus having a plurality of belts mounted for movement about a plurality of rolls, the transport being provided with a plurality of vacuum ports on the lead edge thereof between the rolls, and a plurality of vacuum ports adjacent the rolls beneath the belts mounted thereon, for stripping the lead edge of the copy sheet, the vacuum ports being canted at an acute angle relative to the copy sheet to draw air into the ports in a direction opposite to the direction of movement of the copy sheet.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 3 is a bottom view of the transport assembly of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT For a general understanding of an electrostatic processing system in which the invention may be incorporated, reference is had to FIG. 1. In the illustrated machine, an original D to be copied is placed upon a transparent support platen P fixedly arranged in an illumination assembly generally indicated by the reference numeral 10. While upon the platen, an illumination system flashes light rays upon the original thereby producing image rays corresponding to the informational areas on the original. The image rays are projected by means of an optical system 11 to an exposure station A for exposing the photosensitive surface of a moving xerographic plate in the form of a flexible photoconductive belt 12. In moving in the direction indicated by the arrow, prior to reaching the exposure station A, that portion of the belt being exposed would have been uniformly charged by a corona device 13 located at a belt run extending between belt supporting rollers 14 and 16. The exposure station extends between the roller 14 and a third support roller 15.

The exposure of the belt surface to the light image discharges the photoconductive layer in the areas struck by light, whereby there remains on the belt a latent electrostatic image in image configuration corresponding to the light image projected from the original on the supporting platen. As the belt surface continues its movement, the electrostatic image passes around the roller 15 and through a developing station B located at a third run of the belt wherein there is positioned a developing apparatus generally indicated by the reference numeral 17. The developing apparatus 17 comprises a plurality of brushes l7 which carry developing material to the adjacent surface of the upwardly moving inclined photoconductive belt 12 in order to provide development of the electrostatic image.

The developed electrostatic image is transported by the belt 12 to a transfer station C located at a point of tangency on the belt as it moves around the roller 16 whereat a sheet of copy paper is moved at a speed in synchronism with the moving belt in order to accomplish transfer of the developed image. There is provided at this station a transfer roller 18 which is arranged on the frame of the machine for contacting the non-transfer side of each sheet of copy paper as the same is brought into transfer engagement with the belt 12. The roller 18 is electrically biased with sufficient voltage so that a developed image on the belt 12 may be electrostatically transferred to the adjacent side of a sheet of paper as the same is brought into contact therewith. There is also provided a suitable sheet transport mechanism 19 adapted to transport sheets of paper seriatim from a paper handling mechanism generally indicated by the reference numeral 20 to the developed image on the belt as the same is carried around the roller 16. A programming device operatively connected to the mechanism 20 and the illumination device for producing an electrostatic latent image on the belt 12, is effective to present a developed image at the transfer station C in timed sequence with the arrival of a sheet of paper.

The sheet is stripped from the belt 12 after transfer of the image thereto by a stripper transport 23 and a detack corona emission device 24, to be hereinafter described, and thereafter conveyed by the stripper transport 23 into a fuser assembly generally indicated by the reference numeral 25 wherein the developed and transferred xerographic powder image on the sheet is permanently affixed thereto. After fusing, the finished copy is discharged from the apparatus at a suitable point for collection externally of the apparatus. The toner particles remaining as residue on the developed image, background particles, and those particles otherwise not transferred are carried by the belt 12 to a cleaning apparatus positioned on the run of the belt between rollers 14 and 16 adjacent the charging device 13. The cleaning device, comprising a rotating brush 26 and a corona emission device 27 for neutralizing charges remaining on the particles, is connected to a vacuum source (not shown) for removing the neutralized toner particles from the belt prior to the formation of subsequent images thereon.

Referring now to FIGS. 2 and 3, the stripper transport assembly 23 is comprised of a plenum assembly generally indicated at 30, a stripper roll assembly 32, a rear roller assembly 34, and a plurality of endless belts 36. The plenum assembly 30 is comprised of a top section 38 suitably affixed to a bottom section 40 having elongated slots 42 provided therein. The top section 38 is provided with a conduit 44 which is in fluid communication with the suction side of a suitable vacuum pump (not shown).

The stripper roller assembly 32 is comprised of a stationary hollow shaft 48 having a plurality of roller support elements 50 and a plurality of spacers 52 attached thereto. A conduit 54 in communication with the interior of shaft 48 is adapted for connection to a suitable vacuum source (not shown) to provide a flow of air through the interior of shaft 48.

Each of the roller support elements 50 is provided with a passageway 56 therein communicating with the interior of shaft 48 for passage of air through the perforations in the belts and the passageways 56 into the interior of shaft 48. Each of the spacers 52 is also provided with a plurality of openings 53 in communication with the shaft 48. It can be seen by reference to FIG. 3 that the openings 53 in spacers 52 are provided at the extreme leading edge of the transport while the openings in the roller support elements 50 are provided as close as possible to the small diameter rollers 58 thereon to affect the lead edge of the copy paper as soon as it is in close proximity to the transport.

The passageways or openings 53 and 56 are canted at an acute angle relative to the bottom surface of the transport to provide for a flow of air thereto in a direction opposite to the direction of movement of the copy sheet to be stripped. By canting the vacuum passages in this manner, a substantial improvement in stripping efficiency is obtained. Apparently, the improved efficiency is due to two factors. By reference to FIG. 2A which illustrates the air flow through a port canted in a direction to provide air flow therethrough in the same direction as the copy sheet movement, it can be seen that air is drawn over the top of the copy sheet into the ports. This flow of air apparently puts a downward force on the copy sheet tending to counteract the lifting effect of the vacuum at the mouth of the port. By canting the port in a manner most clearly illustrated in FIG. 2, the flow of air into the ports over the top of the copy sheet is substantially eliminated, thereby eliminating the downward force created by the flow of air thereabove. Further, by providing for a vacuum flow of air toward the lead edge of the copy sheet, the air stream tends to lift the lead edge from the photoreceptor be ized air knife-type stripper at the lead edge of the copy sheet although the problems encountered with an air knife, i.e. possible blowing of air underneath the copies and disturbance of the toner image thereunder is obviated since the air is in actuality not being blown under the copy sheets but is being drawn past the lead edge into the vacuum ports. Thus, by canting the ports in a direction such that the air flow thereto is in a direction opposite to the direction of the copy paper movement, optimum copy paper stripping may be obtained at reduced vacuum levels thereby lowering the power requirements for the vacuum producing device and reducing the noise generated by air flow through the vacuum ports. As a secondary benefit, air flow across the bottom of the corona emission device is minimized thereby reducing the quantity of toner particles drawn into the vicinity of the corona emission device and minimizing toner deposition on the corona emission device elements.

While I have described a preferred embodiment of my invention, it is to be understood that the invention is not limited thereto but may be otherwise embodied within the scope of the following claims.

What is claimed is:

1. In a reproduction machine wherein a transfer member is electrostatically tacked to a moving image support member, the image support member traversing an arcuate path through at least a portion of its travel, a transport apparatus for removing the transfer member from the image support member and transporting the transfer member away from the image support member in a direction substantially tangent to the arcuate path traversed by the image support member including:

a vacuum stripping assembly mounted adjacent the arcuate path traversed by the image support member, the forward edge of said stripping assembly being spaced a minimal distance from the image support member, said stripping assembly having a plurality of air passageways, each of said passageways terminating in a port, said ports being substantially aligned with the leading edge of the transfer member, said passageways being canted at an acute angle relative to the path of movement of the transfer member past said ports, the minimal spacing of said stripping assembly adjacent the support member providing a restriction to the flow of air therebetween into said ports, the canted orientation of said passageways along with the restriction caused by the minimal spacing between the forward edge of said vacuum assembly and the image support member resulting in substantially all of the air being drawn to said ports from a direction opposite to the direction of movement of the transfer member.

2. A reproduction machine according to claim 1 further including a frame member;

a first roll assembly mounted on one end of said frame member, the axis of said roll assembly being disposed parallel to the leading edge of the transfer member adjacent the support member;

a second roll assembly mounted on the other end of said frame member;

a plurality of endless belts operatively mounted for movement around said roll assemblies;

said means forming said air passageways being disposed adjacent said first roll assembly for removing the transfer member from the image support member and engagement of the transfer member with said belts for movement by said belts away from the support member.

3. A reproduction machine according to claim 2 wherein said first roll assembly is comprised of a plurality of spaced rolls in axial alignment, a first portion of said means forming said passageways being disposed to provide ports between said rolls, a second portion of said means forming said passageways being disposed to provide ports immediately behind said rolls beneath said belts, said belts being perforated to allow passage of air therethrough into said passageways.

4. A method for removing an electrostatically tacked transfer member from a moving image support member in a reproduction machine including the steps of:

drawing a plurality of streams of air into vacuum ports adjacent the lead edge of the transfer member, substantially all of the air being drawn in a direction substantially opposite to the direction of the moving transfer member to separate the transfer member from the image support member; and

transporting the separated transfer member away from the image support member. 

1. In a reproduction machine wherein a transfer member is electrostatically tacked to a moving image support member, the image support member traversing an arcuate path through at least a portion of its travel, a transport apparatus for removing the transfer member from the image support member and transporting the transfer member away from the image support member in a direction substantially tangent to the arcuate path traversed by the image support member including: a vacuum stripping assembly mounted adjacent the arcuate path traversed by the image support member, the forward edge of said stripping assembly being spaced a minimal distance from the image support member, said stripping assembly having a plurality of air passageways, each of said passageways terminating in a port, said ports being substantially aligned with the leading edge of the transfer member, said passageways being canted at an acute angle relative to the path of movement of the transfer member past said ports, the minimal spacing of said stripping assembly adjacent the support member providing a restriction to the flow of air therebetween into said ports, the canted orientation of said passageways along with the restriction caused by the minimal spacing between the forward edge of said vacuum assembly and the image support member resulting in substantially all of the air being drawn to said ports from a direction opposite to the direction of movement of the transfer member.
 2. A reproduction machine according to claim 1 further including a frame member; a first roll assembly mounted on one end of said frame member, the axis of said roll assembly being disposed parallel to the leading edge of the transfer member adjacent the support member; a second roll assembly mounted on the other end of said frame member; a plurality of endless belts operatively mounted for movement around said roll assemblies; said means forming said air passageways being disposed adjacent said first roll assembly for removing the transfer member from the image support member and engagement of the transfer member with said belts for movement by said belts away from the support member.
 3. A reproduction machine according to claim 2 wherein said first roll assembly is comprised of a plurality of spaced rolls in axial alignment, a first portion of said means forming said passageways being disposed to provide ports between said rolls, a second portion of said means forming said passageways being disposed to provide ports immediately behind said rolls beneath said belts, said belts being perforated to allow passage of air therethrough into said passageways.
 4. A method for removing an electrostatically tacked transfer member from a moving image support member in a reproduction machine including the steps of: drawing a plurality of streams of air into vacuum ports adjacent the lead edge of the transfer member, substantially all of the air being drawn in a direction substantially opposite to the direction of the moving transfer member to separate the transfer member from the image support member; and transporting the separated transfer member away from the image support member. 